1. Technical Field
The present invention relates to a line recognition apparatus, a line recognition method and a line recognition program that recognizes lines on a surface over which a vehicle is moving based on an image of an area ahead of the vehicle captured by an image capturing unit.
2. Background Art
A target recognition apparatus that recognizes a target based on images of scenes ahead of a vehicle, captured by an image capturing unit, is used in driver assistance systems such as adaptive cruise control (ACC) to reduce the burden on the driver. The driver assistance system can provide various capabilities such as automatic braking and alarm to avoid a collision or reduce the impact at collision. The driver assistance system can further provide assistance in the form of driving speed adjustment to maintain a safe distance to a vehicle ahead, and a lane deviation prevention function that detects the lane on the road surface to prevent the vehicle from drifting into another lane, in which the lane is a line that defines a boundary on the road surface over which the vehicle moves.
JP-3352655-B (JP-2001-092970-A) discloses a lane recognition apparatus that can recognize the lane on the road surface. This lane recognition apparatus includes a stereo image capturing unit that can capture images of scenes ahead of a vehicle, and the captured image corresponding to one screen image is divided into a plurality of areas. Each of the areas is then divided by a virtual horizontal line set on the screen image, wherein the virtual horizontal line can be set based on the distance from the vehicle position, which is computed based on a captured stereo image. Then, based on a luminance image for each area, a luminance edge corresponding to a lane edge is extracted and linear approximation is performed on the extracted luminance edge to recognize the lane image, wherein the lane is a white line.
The lane recognition apparatus of JP-3352655-B (JP-2001-092970-A) extracts the luminance edge in each area of the image obtained by capturing the white line on the road surface, and uses linear approximation on the extracted luminance edge to recognize the white line image on the road surface. However, if the lane curves, the acquired image may be greatly deviated from the actual line, which is not good enough for a driver assistance system.